1. Technical Field
The present disclosure relates to an electrolytic capacitor, particularly to an electrolytic capacitor having a capacitor element that includes both a solid electrolyte and an electrolytic solution.
2. Description of the Related Art
In recent years, along with high performance of electronic devices, a capacitor having high capacitance and small equivalent series resistance (ESR) is required as a capacitor mounted on an electronic device. As such a capacitor, a winding-type solid electrolytic capacitor is used in many cases. A capacitor element included in this winding-type solid electrolytic capacitor has a winding body wound around by a cathode foil and an anode foil on which a dielectric layer is formed. In a winding body is formed a solid electrolyte layer containing a conductive polymer.
Conventionally, for forming a solid electrolyte layer in a winding body, an electrolytic polymerization method, a chemical polymerization method, and the like have been used. Specifically, a winding body is immersed in a polymerization solution for forming a conductive polymer to infiltrate the polymerization solution into a gap present in the winding body. Subsequently, monomers in the polymerization solution are polymerized to generate a conductive polymer in the winding body. However, the method for forming a solid electrolyte layer by using the polymerization solution makes the manufacturing process of a solid electrolytic capacitor complicated.
In such circumstances, as a method for forming a solid electrolyte layer in a winding body, the following processes are proposed (for example, see Unexamined Japanese Patent Publication No. 2008-10657). First, a winding body is impregnated with a dispersion liquid in which particles of a conductive polymer are dispersed or a solution in which a conductive polymer is dissolved, to infiltrate the dispersion liquid or the solution into a gap present in the winding body. Then, drying is conducted to dry the dispersion liquid or the solution impregnated into the winding body. By these processes, a solid electrolyte layer is formed in the winding body.
Further, as to the electrolytic capacitor prepared according to the method for forming a solid electrolyte layer by using the dispersion liquid or the solution, it is proposed that the winding body be impregnated with an electrolytic solution in addition to the formation of the solid electrolyte layer, in order to improve the characteristics of the electrolytic capacitor (for example, see Unexamined Japanese Patent Publication No. 2008-10657).